Devices are known in the prior art which provide an alarm signal when a trailer becomes uncoupled from a trailer hitch. Certain prior art devices include those which have a mechanical switch that is actuated by the trailer when the trailer releases from the hitch. These kinds of devices typically have a switch actuating arm disposed above the ball of a conventional ball-type hitch. If the trailer becomes uncoupled from the ball, the tongue of the trailer which is secured to the hitch flies upward actuating the switch and causing an alarm signal in the vehicle operator compartment.
A trailer hitch monitor device which was adapted for use on a conventional ball-type hitch was shown and described in U.S. Pat. No. 4,127,855 to Toner. Toner provided an electrical circuit for monitoring the connection between a trailer and a trailer hitch. An electrical conductor was connected to the tongue of the trailer and the trailer hitch was grounded. A visual indicator was provided in series between the electrical conductor and a power source to provide an indication of trailer coupling as long as electrical continuity was maintained by the connection of the trailer to the hitch. An audible warning device and switch were in parallel with the visual indicator to provide a warning when electrical continuity was broken.
Unfortunately, this system relied on the use of a solid, conventional ball-type hitch, and consequently all of the electrical portion of the system had to be mounted on the trailer, i.e. the towed vehicle. Thus, the alarm portion of the system was also provided on the towed vehicle, severely limiting the usefulness of such a system.
Meo described a similar type of system in U.S. Pat. No. 4,271,401. This system included a safety trailer hitch with a mechanical connection to connect a trailer to a tow vehicle. Connection was made with the mechanical connection secured by a latch. A backup connection between the trailer and the tow vehicle was releasably secured to the tow vehicle. A first, normally open switch was positioned to be closed when the mechanical connection was made and a second, normally closed switch was positioned to be opened when the latch was closed. A third, normally closed switch was positioned to be opened when the backup connection was secured to the tow vehicle, with the second and third switches in parallel and in series with the first switch. The system further includes an alarm and a source of electric energy in an electric circuit with the switches such that when the first switch and either of the second or third switches were closed, the alarm was actuated. However, as with Toner, the operable portions of the system of Moe had to be mounted to the towed vehicle, substantially limiting the usefulness of the system.
This drawback in the art was addressed by Engle in U.S. Pat. No. 4,593,264. Engle provided a dual trailer hitch warning system for use with a ball and socket trailer hitch. The warning system included an electrically operated alarm system for signaling a loose coupling of the socket member on the ball member. A switch was mounted within the ball member which energized an alarm relay circuit when the ball switch operated due to a loose coupling to complete an alarm circuit between the automobile battery and the horn. The warning system also included a tampering relay circuit adapted to provide an alarm signal if an attempt was made to disengage or short out the alarm circuit or if the socket and ball member were deliberately uncoupled.
Although the Engle system was adapted to provide the electrical alarm portion on the towing vehicle, it still presented a number of drawbacks, including the fact that no means was provided for securely pinning the hitch to the ball, with an alarm means activated by improper pinning of the hitch to the ball. The present invention is directed to solving these and other limitations in the art.